|MadSci Network: Medicine|
Hey, Joe! I'm a physics fan, and usually answer questions about astronomy and physics. But I'm also a volunteer fire fighter with EMT training, and that's why I feel I can answer your question. The information I'm presenting here comes from "Emergency Care Seventh Edition", published by Brady in 1995. It is the standard textbook for EMT-b's. You probably know what wind chill is. Water chill is like wind chill, but much more potent. The human body looses 25 times more heat by being exposed to cold water than cold air. It's even worse if the water is flowing around a person than if it's still, so being immersed in a 30 degree river will cool you down faster than immersion in a 30 degree lake. Surprisingly, the human body can't survive if the core temperature, or the temperature of the internal organs, falls below 80 degrees F. We can walk around outside in temperatures below freezing and be just fine, for short periods of time. Our extremities can get very cold, and we aren't in much danger. But if we get cold inside, our heartbeat becomes erratic, we lose consciousness, and die. Luckily for us, moving around and doing things generates heat inside our bodies. If a man falls into a frozen river, he will try to get out, and the exercize he gets will help keep his core warm. There are too many factors to let us say how long a man can survive in the cold of a frozen river. Some of the variables are the speed the river is flowing, the size of the man, how warm he was before he fell in, how much body fat he has, and what his general health is like. Still, let's hazard a guess, and say that the average sized, healthy man could snorkle in a frozen river for 20 minutes before losing consciousness, and 30 minutes before death occurs. Let's compare that to drowning. Only 10% of drowning victims die from lack of air. The other 90% panic and inhale water, which kills faster than holding their breath does. Even in the lungs are dry and full of air, people die after 4-10 minutes of not breathing. So lack of air would kill a man faster than the freezing water. I hope this answers your question. Layne Johnson
Try the links in the MadSci Library for more information on Medicine.